// max_bytes the cache is a pass-through.
  tf_gcs_filesystem::RamFileBlockCache cache1(1, 0, 0, fetcher);
  tf_gcs_filesystem::RamFileBlockCache cache2(0, 1, 0, fetcher);
  tf_gcs_filesystem::RamFileBlockCache cache3(0, 0, 0, fetcher);
  tf_gcs_filesystem::RamFileBlockCache cache4(1000, 1000, 0, fetcher);
  std::vector<char> out;
  TF_EXPECT_OK(ReadCache(&cache1, want_filename, want_offset, want_n, &out));